Vilyuysky District is an administrative and municipal district, one of the thirty-four in the Sakha Republic, Russia. It is located in the western central part of the republic and borders with Zhigansky District in the northeast, Kobyaysky District in the east, Gorny District in the south, Verkhnevilyuysky District in the west, and with Olenyoksky District in the northwest. The area of the district is 55,200 square kilometers (21,300 sq mi). Its administrative center is the town of Vilyuysk. Population: 25,222 (2010 Russian census); 25,696 ; 28,704 (1989 Soviet census). The population of Vilyuysk accounts for 40.6% of the district's total population.

Zhigansky District is an administrative and municipal district, one of the thirty-four in the Sakha Republic, Russia. It is located in the northern central part of the republic and borders with Bulunsky District in the north, Eveno-Bytantaysky National District in the east, Kobyaysky District in the southeast, Vilyuysky District in the southwest, and with Olenyoksky District in the northwest. The area of the district is 140,200 square kilometers (54,100 sq mi). Its administrative center is the rural locality of Zhigansk. Population: 4,296 (2010 Russian census); 4,312 ; 5,678 (1989 Soviet census). The population of Zhigansk accounts for 79.6% of the district's total population.